Thanks for all the responses. This has not much to do with the skills assessment, that one is done already. For medical people, the 189 documentation says:
Which they very helpfully put under the item "Skills assessment documents". However, to get one of those, you need to have a job offer (which we are still waiting for on paper, we know we have that job, but we need to have a paper trail for AHPRA).
So the question is, can we apply for the visa and add the AHPRA reg later, or do we need to wait for the AHPRA reg to be finalised - basically voiding our current invitation to apply for the 189.